A. Field of the Invention
The present invention relates to a flat lighting device which emits light uniformly throughout the flat lamp surface.
B. Description of the Prior Art
The LCD (Liquid Crystal Display), for example, is not a luminant and, therefore, requires a separate light source to visualize the characters and/or picture displayed by the LCD. Thus a flat lighting device is adopted as a back light for the LCD panel generally.
FIG. 2 shows a flat electric discharge lamp, a kind of flat lighting device 21, disclosed in Japanese Patent Laid-open Sho 61-269848. This discharge lamp 21 of non-circular cross section has a thin and wide discharge tube 22. A fluorescent layer is formed on the inner surface of discharge tube 22, and electrodes 24 are disposed at both sides within discharge tube 22. Magnets 25 arranged on discharge tube 22 form magnetic fields M.
When power is supplied to electrodes 24, electrons discharged between electrodes 24 moves within the electric field formed by the voltage applied to electrodes 24 and magnetic field M formed by magnets 25. Because this lamp 21 needs a high-frequency power source and magnets 25, the lamp 21 has a problem of sophisticated structure. Also because electrodes 24 are subject to collision with the electrons discharged within discharge tube 22 and exhausted thereby, the service life of the discharge lamp is shortened.